Internal combustion engines generate exhaust as a by-product of fuel combustion within the engines. Engine exhaust contains, among other things, unburnt fuel, particulate matter such as soot, and harmful gases such as carbon monoxide or nitrous oxide. To comply with emissions control regulations, engine exhaust must be cleaned before discharging it into the atmosphere. Compliance with the emissions control regulations can require significant changes to existing engine air handling and exhaust after-treatment components and systems or the addition of new air handling and after-treatment components and systems.
The air handling and after-treatment components typically consume a significant volume over the top of the engine. The redesigned and/or new engine components must, however, be accommodated in the same or a smaller geometric volume available around the engine. The volumetric constraints become particularly important for engines used in locomotive or marine applications, where the available space may be further limited. The placement of engine components can also have a significant impact on engine emissions. For example, the air inlet and exhaust locations influence the overall engine configuration when considering the engine orientation as on a locomotive. Locating the exhaust outlet from an after-treatment system too close to the engine cooling radiators or the air intake filters, for example, may allow combustion by-products such as soot to foul the radiators or filter elements. Fouling of the radiators can cause the engines to run hotter, which in turn may cause increased production of harmful emissions such as nitrous oxide. Fouling of the intake air filters may similarly result in incomplete combustion leading to increased levels of unburnt hydrocarbons in the exhaust. Thus, placement of the redesigned and new engine components within the available geometric volume can present a challenge.
One attempt to address some of the problems described above is disclosed in International Patent Application Publication No. WO 2012/093200 A1 of Lundin et al. published on Jul. 12, 2012 (“the '200 publication”). In particular, the '200 publication describes an engine with a twin-turbocharger arrangement positioned at an end of the engine and supported by a common bracket. The '200 publication discloses that the high-pressure turbocharger is smaller than the low-pressure turbocharger and that the turbochargers are arranged so that their rotational axes are orthogonal to each other. Further the '200 publication discloses an intercooler located between compressor stages and a completely separate aftercooler located downstream of a second compressor stage. In addition, the '200 publication discloses that the two turbochargers and the air coolers are designed such that the size of the package is compact, and fits substantially within the width of an in-line engine.
Although the engine system of the '200 publication may include two-stage turbocharging and two-stage intake air cooling, it may still be less than optimal. In particular, because the intercooler and the aftercooler of the '200 publication are separate assemblies, a significant amount of ducting may be required to connect these assemblies to the two-stage turbochargers and other components. This extra ducting may increase costs, decrease performance of the engine, and may make it difficult to access engine components for maintenance or repair. The different sizes of the high-pressure and low-pressure turbochargers may also require unique components for maintenance and repair of each of the two turbochargers, thus increasing the cost of maintenance and repair. Moreover, the arrangement of the two turbochargers may make it difficult to access each turbocharger individually for maintenance and repair. Additionally, the large low-pressure turbocharger, the separate cooling assemblies, and the accompanying ducting may not fit in the space available for certain engine system applications.
The engine system of the present disclosure solves one or more of the problems set forth above and/or other problems of the prior art.